[Xen-changelog] [xen master] x86/VPMU: manage VPMU_CONTEXT_SAVE flag in vpmu_save_force()

[patchbot@xxxxxxx]

commit 028afee0e10af22219efd601ea4016c77324af55
Author:     Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
AuthorDate: Fri Jan 23 17:50:53 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jan 23 17:50:53 2015 +0100

    x86/VPMU: manage VPMU_CONTEXT_SAVE flag in vpmu_save_force()
    
    There is a possibility that we set VPMU_CONTEXT_SAVE on VPMU context in
    vpmu_load() and never clear it (because vpmu_save_force() will see
    VPMU_CONTEXT_LOADED bit clear, which is possible on AMD processors)
    
    The problem is that amd_vpmu_save() assumes that if VPMU_CONTEXT_SAVE is set
    then (1) we need to save counters and (2) we don't need to "stop" control
    registers since they must have been stopped earlier. The latter may cause 
all
    sorts of problem (like counters still running in a wrong guest and 
hypervisor
    sending to that guest unexpected PMU interrupts).
    
    Since setting this flag is currently always done prior to calling
    vpmu_save_force() let's both set and clear it there.
    
    Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
    Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
    Tested-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vpmu.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
index efb2279..e17e194 100644
--- a/xen/arch/x86/hvm/vpmu.c
+++ b/xen/arch/x86/hvm/vpmu.c
@@ -128,6 +128,8 @@ static void vpmu_save_force(void *arg)
     if ( !vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
         return;
 
+    vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
+
     if ( vpmu->arch_vpmu_ops )
         (void)vpmu->arch_vpmu_ops->arch_vpmu_save(v);
 
@@ -176,7 +178,6 @@ void vpmu_load(struct vcpu *v)
          */
         if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
         {
-            vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
             on_selected_cpus(cpumask_of(vpmu->last_pcpu),
                              vpmu_save_force, (void *)v, 1);
             vpmu_reset(vpmu, VPMU_CONTEXT_LOADED);
@@ -193,7 +194,6 @@ void vpmu_load(struct vcpu *v)
         vpmu = vcpu_vpmu(prev);
 
         /* Someone ran here before us */
-        vpmu_set(vpmu, VPMU_CONTEXT_SAVE);
         vpmu_save_force(prev);
         vpmu_reset(vpmu, VPMU_CONTEXT_LOADED);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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